The present invention relates to an external corner formative member, which forms a part of an external corner portion of a building.
In related art of ceramic siding boards for buildings, an external corner post has been employed at an external corner of a building. The external corner post is a member which covers a corner portion of exterior walls to form decorated surfaces with building boards. A fixed interval is ensured by making use of fixtures between side edges of the external corner post and a building board, and after all building boards and external corner posts have been attached to the exterior walls, the interval is filled with sealing compound to prevent leakage of rain water.
In prior art, several kinds of external corner formative member have been proposed (Japanese Patent Unexamined Application H10-280641, Japanese Patent Unexamined Application H10-8683, etc.), which is generally constructed such that it comprises an angled corner plate portion, and a pair of groove portions formed on the opposite sides of the corner plate, respectively. In this case, the external corner formative member is adapted to be attached to an external corner portion of a building in such a manner that the side edge portion of a building board to be attached as a siding board is fitted in the groove portion thereby to allow the side edge portion of a building board to be covered by the external corner formative member, and at the same time, the external corner portion of a building is also covered by the angled corner plate portion.
When an external corner formative member of this kind is employed, an external corner post that has been formed of the same kind of material as that of the building board is no more required to be employed, and at the same time, the work of filling a sealing material is no more required, thus making it possible to simplify the constructing work of the external corner portion of a building.
However, when the external corner portion of a building is constructed using this conventional external corner formative member, the side edge portion of a building board is simply fitted in the groove portion of the external corner formative member without performing a work to fill the groove portion with a sealing material. Therefore, rain water is more likely to be allowed to pass through a gap formed between the front plate portion of the groove and the building board inserted therein, and then to penetrate, while turning around the side edge of the building board, into the inner side of the building board, thus causing the building frame to become wet with rain water.
With a view to prevent rain water from penetrating into the groove portion, there has been proposed an idea to internally bend the side edge portion of the front plate portion of the groove so as to make the bent portion function as a kind of weir, or an idea of forming a plurality of lips on the back plate portion of the groove so as to make the lips function as a sort of weir. However, when the present inventors have conducted a leakage test on the external corner formative members constructed based on these ideas by making use of a hose for showering, these external corner formative members are found insufficient in water leakage prevention.